2 answers

The links suggested in the answer, give enough information to make the update, but for the beginner in OpenStack (like me), more information is needed.
I share some notes on which successfully realize the update (based on http://docs.openstack.org/openstack-ops/content/ops_upgrades-general-steps.html (http://docs.openstack.org/openstack-o...) ):

Perform some "cleaning" of the environment prior to starting the upgrade process to ensure a consistent state. For example, instances not fully purged from the system after deletion might cause indeterminate behavior.

Keystone: The keystone CLI is deprecated in favor of openstack, the Common OpenStack client supporting multiple services. If you have custom scripts using keystone CLI command, you must adapt them.

Develop an upgrade procedure and assess it thoroughly by using a test environment similar to your production environment.

You can perform an upgrade with operational instances, but this strategy can be dangerous. You might consider using live migration to temporarily relocate instances to other compute nodes while performing upgrades.

The following order for service upgrades seems the most successful. Try it, or use full upgrade:

Identity Service (keystone)

Image service (glance)

Compute (nova), including networking components

Block Storage (cinder)

dashboard

Make a full database backup of your production data. As of Kilo, database downgrades are not supported, and the only method available to get back to a prior database version will be to restore from backup.

Take down all the services, or by services(using the order mentioned above), and upgrade to kilo

yum upgrade

Upgrade services configuration, and databases

keystone:

Update db

keystone-manage db_sync

Install common Openstack client:

yum install python-openstackclient

Keystone use httpd mod_wsgi. You must to do configuration changes in httpd, according to install guide: http://docs.openstack.org/kilo/install-guide/install/yum/content/keystone-install.html (http://docs.openstack.org/kilo/instal...)

Comments

Thanks for your answer.
I expected to find a formally documented Upgrade Guide.
It seems for now is a process of collecting small pieces of information to build the road. (At least for a beginner like me, where the steps are not obvious)